While soloing the munitions factory today, I was just in the process of stepping on the end of level elevator when my router decided it should boot my connection out. When I fixed it, the game was back to the title screen, but with the end of level overlay. Needless to say, I couldn't interact with it because I wasn't logged in, so the descend option would obviously point to nothing, and the interface itself has no ability to be closed, so I had to restart the game. I have not attempted to reproduce it, but I assume this behavior would occur again if you disconnect during this time.

Attached is a picture of what I experienced.
http://i.imgur.com/UY3gQ.png

The worst part of this was that when I logged back in, I was back in the mission lobby, meaning I lost the progress of my run. Particularly annoying because I had just revived, but it was only 5 energy lost, so whatever.

Anyways, thank you for your time, and keep up the great work!